Under audiometry refers to a medical procedure for measuring the level of human hearing, which is characterized by the completeness of the biofunctional susceptibility of the human hearing analyzer and the occurrence of abnormalities in the anatomical structure. The term "audiometry" was formed by the merger of two words - Latin audio (hear) and Greek metreo (measure).
To check your hearing and perform audiometry, you need to consult a otolaryngologist (ENT doctor), a functional diagnostic doctor.
Principle and features of the procedure
A person with a healthy ear perceives well both spoken language and speech that others utter in a whisper. But sometimes this sensitivity can be reduced and a quieter speech or whisper a person stops hearing. This is due to injuries, birth defects, occupational activities that affect hearing, and diseases. To assess the susceptibility of different pitch sounds in medical circles and audiometry of hearing is used.
The hearing audiometry technique helps to recognize the threshold of perception of sounds for each specific patient at a specific point in time. The procedure is very simple and does not require the presence of complex equipment. All the equipment used in audiometry is tuning forks and audiometers.
The main criterion for the norm of hearing is the ability to recognize the whisper of a person who is pronounced six meters away from the ear being studied. When used during audiometer testing, it is possible to identify both the sensitivity level of hearing and the place of damage in the body, which interferes with the normal functioning of the hearing aid.
Audiometry is very simple. In the auricle, which is currently subject to investigation, an audible signal is given by the doctor required to determine the state of frequency and strength. If the patient perceives the signal (that is, hears), he presses the button; if he does not recognize, he does not. This process perfectly characterizes the threshold of hearing.
When conducting computerized audiometry, the patient should fall asleep. On the eve of his head are fixed special sensors that perceive changes in the power of brain waves. The computer with the help of special electrodes helps to independently monitor all the brain reactions of the patient and build a diagram based on them.
The indications for the procedure for measuring the level of hearing are:
- chronic or acute deafness;
- middle ear inflammation - otitis media;
- the process of selecting a hearing aid for a patient;
- verification of the effectiveness of the therapy.
Audiometry has no contraindications. It can be done at any time, while the patient does not feel any discomfort or pain. By the time the process lasts about half an hour.
There are many types of modern audiometry, it can be:
- above the threshold;
Conducting tonal audiometry
In order to more accurately measure the patient's threshold for sound perception, a specialist conducts hearing tests in the range from 125 to 8,000 hertz. With tonal audiometry, it becomes possible to determine the minimum and maximum sound levels that are comfortable for the examined person.
An audiometer is used during this procedure, where, using headphones that are connected to the device, a specific tone is sent to the auricle. If the patient has heard the signal, he presses a special button, and if this does not happen, the tone of the signal rises. This happens right up to the moment when the signal becomes audible and the patient presses the button. This indicator is the lower limit of the patient's hearing level. The maximum level is determined in exactly the same way.
Tone audiometry can be used for any age of patients, but for children the game form is more suitable. As a result of the study, the specialist receives an accurate and complete picture of the patient's hearing parameters.
Features of the threshold technique
Threshold audiometry is performed using an audiometer. The minimum frequency of the apparatus is 125 hertz, and then it will increase with a run-up of 67.5 hertz to the maximum frequency provided for by a particular audiometer model. A similar procedure is carried out in a soundproofed room. If such conditions are not created, the specialist must take into account the effect of external noise on the test results. In order to smooth out such imperfections of the procedure carried out, in-ear telephones are often used, which can improve the accuracy of studies to identify the level of hearing.
The advantages of the in-ear phones are the possibility of reducing outside noise, reducing the need for masking sounds due to inter-atomic relaxation, eliminating the collapse of external auditory passages. Of particular importance are the advantages of playing with newborns. The accuracy and regularity of repetition of the results suggests that this technique can be considered very reliable. At the same time, analyzing the schedule of individual air permeability, the specialist has the opportunity to draw conclusions about the level of functioning of the middle ear and its condition.
With complete deafness, this technique does not immediately reveal the site of the lesion; to determine it, it is imperative to carry out additional threshold tests. Among such techniques, Fowler or Langenbek tests and various noise techniques are especially popular. These types of tests will clarify for specialists where the damage is located - in the ear maze, in the cells of the pre-door or auditory nerve.
Use of computer and speech audiometry
Computer audiometry is the most accurate method for determining hearing acuity. Computer equipment gives the patient complete freedom of action and movement, he can relax and not focus on how to hear certain sounds in a timely manner. The equipment itself is able to determine all limit values, it acts absolutely painlessly and safely, so this method is widely used to make an accurate diagnosis, even in newborns.
With speech audiometry, on the contrary, all actions are carried out exclusively by the patient and the doctor without the use of any technical means and devices. This is the most ancient method for determining the hearing threshold. The result of this procedure can be largely determined not by hearing, but by the intellect and vocabulary of a sick person. Such a technique can produce different results when the audiometrist pronounces individual words or their composition into sentences. Sentences are always better perceived by patients and easier to distinguish.
Modern medicine practically does not use a similar technique. It is used today only in cases where specialists need to test a patient to select a suitable hearing aid for him.
Features objective audiometry
The objective technique is used in newborns and in the forensic industry. It is based on the analytical features of the conditioned and unconditioned reflexes of the human body, which must respond to audio stimuli of different frequencies. The reactions of the organism can be recorded with this method for reasons independent of the will of the organism being studied.
Among the unconditioned reflexes that are considered with objective audiometry, one can distinguish dilating eye pupils or a cochlear-pupillary reaction, closing eyelids with sudden sounds or an auropalpebral reflex, inhibition of sucking in a newborn with different sounds, contractile ability of the ocular muscle of the eye, galvanic skin changes, reactions vascular system.
Modern objective audiometry is subdivided into acoustic impedance measurement, which includes the registration process of the acoustic reflex, and tympanometry, electrocholeography, and electroencephalaudiometry. At the same time, tympanometry helps to assess the mobility of the eardrum, the chain of the bony part of the patient's hearing aid, and with the help of an acoustic reflex, the signal from the intra-aural muscles is recorded as a response to the impact on the patient's eardrum. Electrocochleography allows you to electrically stimulate the auditory nerve, while electroencephalaudiometry demonstrates to the physician the potential of the brain's auditory zone.
Game audiometry is used to a greater extent when working with a child category of patients. Reflectingly pushing lifeless buttons on children for a long time cannot, therefore, the technique uses the principle of using game moments. For example, when the sound is heard and the button is pressed while doing this, a small patient will be able to see a new bright picture or some game object that will stimulate him to carry out the audiologist's commands.
When playing audiometry, a tone audiometer is often used, which was once suggested by the specialist Jan Lesak. The audiometer is a toy house with humans, animals, vehicles. The patient is given a remote control in the form of a fungus, with which he can perform certain actions under the right conditions. For example, in order to free a little man from captivity, a small patient must wait until he is asked to do so and press the corresponding button on the fungus. So audiometrists understand that his signal was heard by a child. A similar technique is proposed by doctor Kosachev, there are also methods for determining hearing in young patients, tested by other specialists in the industry.
The importance of audiometry in children is expressed in the fact that with a poor level of hearing, children have a delay in speech development.
Method of suprathreshold audiometry
The above-threshold method of testing hearing acuity was proposed and tested by Luscher. Thanks to this method, experts now have the opportunity to evaluate the differential threshold of sound power - the index of small intensity gains. This study is most often carried out if there is a risk of an increase in the volume of lymph in the cavity of the inner ear (Meniere's disease), auditory neuroma (benign neoplasm, the source of which is the auditory nerve). The technique of suprathreshold audiometry with unilateral hearing loss is used, but it can also be used with bilateral anomalies of the hearing aid. At the same time, a certain sound signal will be sent to each ear, which should correspond to the threshold norm of a specific hearing aid. For example, if on one ear the threshold value should be equal to 5 dB, then on the second - the acceptable value can be equal to 40. At the same time, the signal that arrives at the diseased ear gradually increases by 10 decibels, and the boundary sound value supplied in a healthy ear, they are brought in such a correspondence that the patient feels that a signal of a single intensity is given in both ears. This is the equalization of the tonality with a gradual gradation of one threshold equal to 10 decibels.
Use of screening audiometry
Today's medical audiometer can be represented by three types of devices - polyclinic, screening, or clinical. The simplest device is a screening audiometer, which provides a specialist with a much wider field of possibilities during the procedure than the same outpatient apparatus.
Tone diagnostics of audibility is made in this case according to the sound conductivity of air masses. A screening audiometer is a mobile device, its functionality will allow a specialist to individually select the frequency and tone of the sounds produced. At the same time, it is possible to test a patient both manually and automatically.
During testing, a parallel-connected otolaryngological apparatus will help assess the levels of hearing and sound comfortable for the patient. With the help of a connected microphone, the doctor has the opportunity to contact the patient, and with the help of a printer there is a chance to get an audiogram in printed form.
Cabinet and results of the procedure
In order for the results of audiometry to be objective, the procedure should be carried out in a well-isolated room, where the parallel influence of external noise on the process is minimized. Also, the space where the examination takes place must be protected from electric and magnetic waves.
The room should be free, especially when using the speech method, when the distance from the patient to the doctor must be at least 6 meters. The best venue for this diagnostic is a specialized acoustic chamber, which is adapted for audiometry.
After the procedure, the specialist receives several special graphs on two-axis planes. On the horizontal axis are the divisions, expressed in hertz, and they characterize the frequency of tones. The vertical axis shows sound intensity in decibels. The sound perception of the right ear is shown on the curve of red color, on which there are circles, and of the left one - on the blue curve with crosses.
Solid graphs demonstrate air conduction, and dotted ones show bone.
The numerical data of hearing levels grows ascending on the graphs, which indicates that with a lower indicator of a similar magnitude, the maximum deviation from the norm is recorded, that is, the patient hears as poorly as possible in this case. The decoded graphs of audiometry allow audiologists to determine both auditory thresholds and sites of pathology localization, setting diagnoses and prescribing therapy with maximum accuracy.